Self-checkout system



FIG. 1 is a front, top and left side perspective view of a self-checkout system showing my new design;

FIG. 2 is a front view thereof; and,

FIG. 3 is a left side view thereof.

The bottom and rear views of the self-checkout system are non-ornamental and have not been claimed. The broken lines shown in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a self-checkout system, as shown and described. 